Meniscus

This is the curved surface of a liquid. We usually observe the meniscus of an aqueous solution in glassware. Here we see the water creep up the glass due to the attraction between the two substances. When reading the level of a liquid in a measuring device, we always read to the bottom of the meniscus. This is made more difficult if the glassware is dirty, as there is less attraction to the glass and the meniscus will be irregular, reduced or absent. Be careful when making observations, as students can mistake the meniscus for a thin layer of another substance.

Liquid mercury metal has a greater attraction to itself than the glass. Consequently, its meniscus is unusual as it curves upwards.